Figure 2. Proliferative diabetic retinopathy epiretinal membranes. A: A negative control slide that was treated with an irrelevant antibody showed no labeling (original magnification 40X). B: Immunohistochemical staining for CD31 showing blood vessels positive for CD31 (original magnification 40X). Immunohistochemical staining for cathepsin L showing immunoreactivity in vascular endothelial cells (arrows) and stromal cells (arrowheads). C: Low power (original magnification 25X). D: High power (original magnification 40X).